1. Field of the Invention
The invention relates to a dental implant and conversion assembly, and in particular to an improvement in the shock absorption and force distribution qualities of the dental implant assembly in the section of the assembly which is located between the gum line and the jaw-bone. The invention further relates to a conversion assembly for converting various types of implants for use with the assembly according to the invention.
2. Description of the Prior Art
Dental implants have become very popular in recent years as the modern method for replacing missing teeth, often eliminating the need for extensive bridge work or even dentures. Partial dentures can very easily be replaced by structures supported on implants. It is also known, in partially edentulous situations, to support a bridge on an implant and a natural tooth.
Implant surgery usually entails the following procedures: Firstly, an incision is made in the gum tissue, and the jaw-bone is revealed. Secondly, a hole is drilled in the jaw-bone. This may be done with a dental drill, at a drilling speed which ensures that the surrounding bone tissue is not damaged. Thirdly, an implant fixture is screwed into the hole in the jaw-bone so that its top is approximately flush with the jaw-bone. Such fixtures are usually made of titanium, and various lengths and diameters are commercially available.
After a period of several months, during which the implant fixture is allowed to osseointegrate with the jaw-bone tissue, the dental technician or dentist attaches certain other components of the assembly, such as an abutment section which extends substantially through the buccal mucoperiosteum, i.e. from the jaw-bone to the gum line. A dental prosthesis, such as a crown, a bridge or a full denture, may then be attached at the top of the abutment section.
One of the main concerns in the early development of dental implant technology was the question of whether or not an implant could withstand the intense forces which act on teeth or fixed dentures. Further developments and research, in particular in Sweden, showed that several dental units could be securely mounted on implants.
It had been known that the bone tissue in the jaw-bone were not as densely packed as other bone structures, such as for instance the forearm bones. Accordingly, a major problem associated with early implant assemblies, was the lack of absorption and deflection they provided for forces acting on the dental prostheses.
Several improvements in that respect have been suggested, such as that in U.S. Pat. No. 4,746,293 to Lundgren et al. Regarding the use of the Lundgren et al device for oral prostheses, an 0-ring of resilient material such as rubber is disposed directly below the attachment patrix for a prosthesis. The 0-ring serves as a type of shock absorber and also allows for slight deflection of the axis of the patrix with respect to the longitudinal axis of the assembly.
U.S. Pat. No. 4,772,204 to Soderberg, similar to the above Lundgren et al device, provides for two 0-rings to be disposed directly below the denture or crown, i.e. in the vicinity of the gum-line.
Several further devices have been proposed which facilitate restricted shock absorption and movement of the denture with respect to the jaw-bone. However, all such devices provide for the shock absorption means to be disposed in the vicinity of the gum-line, which leads to problems especially with the local hygiene as well as with the aesthetic appearance of the prosthesis.